Back in the day at the Kodokan, I was told of a famous judo athlete who said he only "did" judo. When seen pushing huge hunks of steel in the Kodokan weight room, and quizzed about this, he said "this is judo preparation" or something like that.
Going for a run is cross-training. So is the weight room. So is trying another martial art, going for a swim, hiking, rowing, or whatever, including even target shooting for concentration skills. It all adds up.
W